The phased array radar utilizes a phased array antenna made by arranging a plurality of antennas corresponding to a plurality of channels. In the phased array antenna, giving phase differences to a plurality of transmission signals for transmission from the plurality of antennas makes it possible to emit radio waves in a desired direction. Further, giving phase differences to a plurality of received signals enables the realization of a reception antenna having directivity in a desired direction.
Emitting radio waves in a desired direction requires accurate control of the phase and amplitude of transmission signals in the respective channels. In order to achieve accurate control of phase and amplitude, the phase value settings and amplitude value settings of these channels may be adjusted in order to perform channel correction (i.e., zero-point correction) in advance, such that phase differences and amplitude differences between the channels are precisely equal to zero.
In the related art, zero-point correction is performed by utilizing a mixer to detect a phase difference and a diode to detect an output power difference between two adjacent channels. An attempt to take measurements and make adjustments simultaneously in a parallel manner with respect to all the channels, however, gives rise to a problem in that the identity of a signal serving as a reference for phase and amplitude correction becomes obscure. In such simultaneous, parallel measurement, signals leaking through couplers that connect the channels to the mixer or connect the channels to the diode may cause significant interference between the channels, which results in the difficulty of making a correction having a basis on accurate references. Rather than in a simultaneous, parallel manner, two adjacent channels may be successively selected for comparison with each other in a consecutive manner. Such an arrangement, however, may create a problem in that the correction of a large number of channels becomes time consuming.